PDO multiple queries work except for SELECT query

Question

I have a query in PDO which contains multiple actions. I first looked at this question to know wether or not multiple queries are even possible.

My code looks like this:

$stmt = $db->prepare(
    "UPDATE 
        tbl_user_dashboards
     SET 
        is_active = 0
     WHERE 
        id_user_key_fk = 1;
     INSERT INTO 
        tbl_user_dashboards(id_user_key_fk, dashboard_name, dashboard_description, is_active)
     VALUES 
        (1, 'bla', 'blabla', 1);
     SELECT
        id_dashboard AS did,
        dashboard_name AS dname,
        dashboard_description AS ddesc,
        is_active
     FROM
        tbl_user_dashboards
     WHERE
        id_user_key_fk = 1
     ORDER BY
        id_dashboard ASC;"
);
$stmt->execute();

$data = array();
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
    $data[] = $row;
}

My problem is, is that the UPDATE and INSERT work fine, but the SELECT doesn't work (my JSON object stays empty and I don't get any errors, just [] as my output).

When I isolate the UPDATE and the INSERT and run the SELECT as a seperate statement after the UPDATE and INSERT, then it does work but that's not my preferable solution.

Any thoughts on this?